In our current study we are attempting to determine if the decrease in enzyme activity during transit from the duodenum to the ileum is secondary to intraluminal proteolytic digestion. Hence, we are stimulating exocrine pancreatic secretion in normal subjects with cholecystokinin and monitoring the activities of trypsin, amylase and lipase in the duodenum, jejunum, and ileum after the addition of trypsin inhibitor or chymotrypsin or trypsin.